Method of treating tobacco and product resulting therefrom



Patented July 2, 1935 UNITED STATES METHOD OF TREATING TOBACCO PRODUCT RESULTING THEREFROM Charles Dunn, Lock Haven, Pa.

N Drawing. Application May 1 8, 192?;

Serial N0, 192,480

. '1. Claims. (01. 167-3 1) This invention relates to the treatment of tobacco for use for insecticidal purposes, especially, although not'exclusively, for'use in the manufacture of dry insecticide powder or dust, and

. to the resulting product, and has for itsgeneral objects to increase the insecticidal properties of such material and to render the same more eflicient andmore convenientlyavailable .for use.

Insecticides having tobacco as their base, or nicotine insecticides as they are called, have been of two types, namely, liquids, which have been applied by spraying, and dry p wders, which are applied by dusting. The latter type has many advantages over the former, among which may be mentioned its light weight, the quickness with which it may be applied over a wide area, its availability, for this reason, for use in emergencies and for purposes where liquid spray would V a commercial nicotine: salt, while liquid sprays be practically useless, and the fact that no water supply is necessary for its preparation and use. For the killing .eifect of tobacco insecticides as such, whether liquid or dry, reliancehas hitherto been placed solely upon the toxic action of nico tine, although for special purposes such insecticides have in some instances been usedin combination with other insecticidal materials. Nicotine dusts have usuallyconsisted of tobacco powder, either pure or mixed with other finely ground material as a filler to increase the bulk, or of a suitable pulverulent carrier impregnated with have-consisted primarily of solutions of such a salt, usually nicotine sulfate, or of tobacco powder carried in suspension in water or other liquid. Tobacco powder or dust. has heretofore. been prepared by-curingthe tobaccoin the usual way, drying, and pulverizing ina suitable grinding mill.l The ordinary curing; method maybe described'asa process of starvation in which the cellular-construction is notdestroyed and there is a translocation. of mobile nutriments which takes place progressively from the outer parts of theleaves, thenceto the veins and stems, and eventually to the stalk, ,At the same time there occur certain"bacterio1ogical and ,chemical changesin the course ofwhich the starches are converted into sugars. These changes, which are in thenature of fermentation, are essential to the proper preparation of tobaccofor its ordimoisture without which the bacteriologicalactionwillnottake place. It is therefore custom- 'sons hereinafter explained.

ary to carry on thisproce ss at temperatures ranging from 40 F, to 80 F., in the case of natural curing, or at a slightly higher temperature in the case of flue-curing (usually about 20 F.

higher than the outside air), but the temperature 5, V

is never permitted materially to exceed 110 F., at least until. the curing processes are well advanced, in order to avoid modification of the cellular structure of the leaf and insure the initiation' of the translocation processes necessary to normal curing. The proper curing of the tobacco by the natural process usuallyrequires from three to eight weeks, while theflue method usuallyrequires a cure of at least one week.

. The bacteriological conversion of thestarches of the tobacco into sugars is accompanied by a loss of nicotine, which is not objectionable when the tobacco is to beused for its ordinary purposes, but which is distinctly undesirable where it is desired to retain the toxic qualities of the nicotine for insecticidal purposes. Also the translocation process above referred to tends to drive the nicotineirom the leaves toward the stalks and to increase the nicotine content in the latter, at the expense of the former, whereas, in the preparation of an insecticide dust, retention of the nicotine in the leaves is desirable for rea- It has been discovered that the insecticidal value of tobacco is not confined to the toxic action of the nicotine, but that the tobacco contains certain oils, waxes, gums, and resins, the exact composition and action of which are not at present very clearly understood, but which are known to have a .direct insecticidal effect in proportion to the amounts. present. Moreover, the adhesive qualities'of certain of these substances contribute 'materially tothe insecticidal action of an insecteriological action incidental to the usual process of curing and are therefore not materially present in insecticides made ,from ordinary tobacco dust. On the other hand, these substances are almost 5 totally absent frominsecticides prepared from commercial'nicotine salts. f

' The present invention has for an object to; effect the treatment of natural tobacco in such a manher as to preserve the full nicotine content, especially in the leaves, avoid any loss of the resinous and oleaginous components, and put the same into such condition that it can be readily reduced, by grinding or otherwise to'a perfectly dry,- impalpable powder which can be readily projected,

as by a blower, in the form of a light, extended dust cloud which, in a still atmosphere, will hang for a considerable time over an orchard or other area to be treated and gradually settle evenly upon the trees or plants, completely enveloping and closely adhering to any insects thereon. To this end the invention contemplates killing the tobacco quickly, and before the toxic content thereof has been materially reduced, as by subjecting it for a relatively short time to a temperature sufficiently high to dry the same, check the translocation process, and kill the enzymes or ferments, thereby preventing bacteriological action, as well as to oxidize the resinous and oleaginous materials, but not sufficiently high to ignite or char the tobacco or to drive off the volatile oils. In this manner the loss of nicotine, oils, gums, etc., due to fermentation, is avoided (such fermentation, which is desirable in the curing of tobacco for ordinary purposes, not being necessary in the case of tobacco used as an insecticide), the full nicotine content retained in the leaf tissues, and the whole, including the oils, etc., put into such dry and fragile form as to permit the same to be readily reduced, as by grinding, to the desired impalpable powder or dust.

The tobacco used is preferably the species known as Nicotiana Rustica, which is relatively rich, not only in nicotine content, but in the oils, resins, etc., above referred to, and which is believed to contain other alkaloids of decided toxic value. In this species the nicotine content has, by suitable cultivation, been brought up to 4% or 5%, and in some specimens to 7% or more, while the resinous and oleaginous substances referred to run from 8% to 12%, and, in the case of the 7% nicotine specimens, considerably higher. This plant, in its raw or uncured condition, direct from the field, is preferably placed in a suitable kiln or oven and subjected, in a substantially dry atmosphere, to a temperature in excess of 110 F., which is the maximum at which ordinary curing is carried on, but not in excess of 450 F., above which point the leaves begin to char. The temperature employed is preferably at least 120 F. in order to insure drying and oxidation of the oils, gums, etc., and preferably not over 400 F. in order to avoid vaporization of their more volatile components. In practice, the temperature to which the tobacco is subjected should-be as high as can be maintained without volatilization of the oils and varies considerably in difierent species of tobacco and even in different specimens of the same species. This treatment is continued until the tobacco has been thoroughly dried, the time required depending upon the condition of the tobacco and the temperature employed. If, as is preferred, the tobacco be subjected to a temperature approaching 350 F., thetreatment may be completed in thirty minutes, and at all events the temperature is maintained sufficiently high to cause the thorough drying of the material in not more than two or three hours. This treatment can therefore be carried on as a continuous process by passing the tobacco through the kiln or oven on a slowly moving belt.

After the tobacco has been thoroughly dried, as above described, it ispreferably first reduced to a comminuted condition, as by passing the same through a rotary cutting machine, and is then ground toan impalpable powder in a suitable attrition or impact mill, after which it is bolted or sifted through a fine screen having at least meshes to the inch. It is practically impossible to grind the wood fiber and pithy material of the stems and stalks to the fineness required of an insecticide powder or dust, and the screening operation serves to separate this imperfectly ground material from the pulverized web of the leaf and the pulverized skin of the stalks and stems. Due to the relatively high temperature to which the tobacco has been subjected, the translocation process, incidental to ordinary curing,,is prevented, so that the nicotine is not driven from the leaves into the stems, which, in their natural original state, contain very little nicotine, with the result that practically all of the nicotine is retained in the dust and practically none'is lost with the coarser material which is screened out. Also, the oxidization of the resinous and oleaginous materials, which occur principally in the leaves and in the skin of the stalks and stems, makes it possible to separate these materials from the woody parts by attrition or impact and to grind them to the requisite degree of fineness; something which it is impossible to do in the case of tobacco cured in the usual manner. Asa result, the proportional content of nicotine and of resinous and oleaginous matter in the dust produced is relatively greater, rather than less, thanin the natural tobacco. Thus, for example, if a tobacco having an original nicotine content of 5% and an original content of oils, gums, resins, etc. of 10% has sifted from it 25% of material containing virtually none of these in redients, it will be seen that the residue will contain 6 5% of nicotine and l3 of resinous and oleaginous matter.

The powder thus produced may be used as an insecticide dust either without further treatment or with the admixtureof other materials to increase its bulk, promote the toxic action of the nicotine, or adapt the same to special conditions. If desired, the nicotine content may be increased and standardized by the addition of nicotine sulfate or other nicotine salt, while the content of resinous and oleaginous material may be similarly increased and standardized by the addition of these materials recovered from extracts thereof made from other tobacco.

It will be seen that the characteristic feature of the invention above described resides in the treatment and desiccation of raw or uncured tobacco, direct from the field, and without any preliminary curing whatever at an initial temperature materially higher than that permissible in standard curing practice, with the consequent prevention of the translocation and other processes necessarily incidental to normal curing, the retention of the normal nicotine content in the leaf tissues, the oxidization of the resinous and oleaginous materials, and the reduction of the whole to a condition in which there can be readily produced therefrom a fine dust or powderhaving a maximum content of the elements desirable for insecticide purposes. This is not to be confused with processes, heretofore proposed, of subjecting partially cured tobacco to relatively high temperatures for the purpose of improving its grade, color, flavor, aroma or other qualities. I am aware, for example, of the process described in the patent to Benjamin, No. 1,224,703, May 1, 1917, wherein the tobacco is subjected to an initial temperature of approximately F. for a period of from one to three hours, or until the major portion of the moisture has been removed, after which the temperature is raised, through several successive stages, to between 200 F. and 225 F. In this, as in all other similar processes of which I amaware, the real or initial curing of the tobacco takes place in substantially the usual manner at a relatively low temperature prior to the application of the special heat treatment in question, and during this preliminary curing care must be taken to avoid desiccation, checking of the translocation processes, or destruction of the cellular construction. of the leaf. In the'present process in which the tobacco, without preliminary curing, is directly subjected to the high temperature, some modification of the cellular structure is modified, but this, while fatal to tobacco intended for ordinary uses, is not objectionable in the case of tobacco employed for insecticide purposes.

While the preferred mode of practicing the invention has been described herein with considerable particularity, it will be understood that this has been done for purposes of exemplification merely, and that said invention, as defined by the claims hereunto appended, may be otherwise practiced Without departure from the spirit and scope thereof. It will also be understood that, While the product is especially well adapted for use as a, dry insecticide dust, its utility is by no means limited tothis particular field, and that the finely ground. tobacco may be employed as a source of nicotine in liquid sprays, and for other purposes. y

The term tobacco is herein used for convenience to designate generally plants of the Nicotiana family, such, for example, as Nicotz'ana, rustica, which are characterized by a natural nicospecies least suitable for the latter purposes, be-f cause of their high toxic content, are, for that reason, best suited for the production. of insecticides in accordance with my invention.

Having thus described my invention, I claim:

1. The hereindescribed method of treating tobacco which includes subjecting the raw or uncured tobacco toa temperature of approximately 350 F. before the toxic content of the raw tobacco has been materially reduced. a

2.. The process of treating tobacco which includes heating tobacco immediately after harvesting to a temperature of at least C. to dehydrate the same and reduce the moisture content 7 of the tobacco to less than 15% thereof.

3. The process of treating tobacco which includes heating tobacco immediately after harvesting to a temperature of at least 60 C. for less than five hours and more than one half hour to dehydrate the same and reduce the moisture contentof the tobacco to less than 15% thereof.

4. Themethod of preparing insecticides and the like from plants of the Nicotiana family which includes arresting biological changes in the plant by subjecting the same, before such changes have taken place to any material extent, to an initial temperature materially in excess of F. and thereafter dehydrating the same.

5. The method of preparing insecticides and the like from plants of the Nicotiana family which includes arresting biological changes in the plant by subjecting the same, before such changes have taken place to any material extent, to an initial temperature materially in excess of 110 F.. and thereafter completely desiccating' the same.

6. The herein-described method of treating tobacco which includes subjecting the raw or uncured tobacco,.before the toxic content thereof has been materially reduced, to an initial temperature materially in excess of 225 F. and there- CHARLES DUNN. 

